Journal of Superconductivity and Novel Magnetism最新文献

To provide candidate materials for the high-field winding-package (WP) of the toroidal field coil (TF) in next-generation Chinese compact burning plasma tokamak, Western Superconductor Technology Co., Ltd (WST) has newly developed a type of high J_c Nb₃Sn wire with restacked-rod process (RRP) of the distributed barrier layout. To avoid the conductor degradation during electromagnetic and thermal cycling, the high-field WP is designed as a short-twist-pitch (STP) cable. After cabling and compaction of conductor, the STP design can cause severe indentation damage to the strands. The indentation not only impact the transport performance of the strand, in the meantime impact the thermo-magnetic stability. To investigate the effect of indentation on the performance for the WST high J_c Nb₃Sn strand, series measurements were carried out. In this paper, the critical current (I_c) measurement, residual resistance ratio (RRR) measurement, magnetization measurements, and V-I tests were performed on indented samples, and the results were compared with other two types of high J_c Nb₃Sn strands used in high-field WP. It was shown that the critical performance of the samples decreased significantly at an indentation depth of 0.4 mm, and the RRR value decreases with increasing indentation depth.

This study investigated the structural, electronic, optical, thermodynamic, and thermoelectric properties of the Bi₂Se₃ compound when strains along distinct crystallographic directions. This compound showed a p-type semiconductor nature with a bandgap of 0.77 eV. The anisotropic behavior of the material has also been examined, providing insights into potential applications in various fields. We employed the density functional theory (DFT) under the Wien2k package. The calculations utilized the LSDA (local spin density approximation) and mBJ (modified Becke-Johnson) local density approximation functionals to handle exchange–correlation interactions. The study covered a range of characteristics, including heat capacity, Debye temperature, lattice thermal conductivity, and optical properties including the absorption coefficient, the electron energy loss, the refractive index, and the optical conductivity as well as the dielectric tensor’s real and imaginary components. The thermoelectric properties including the Seebeck coefficient, electrical conductivity, electronic contribution to thermal conductivity, and calculated power factors have been deduced and discussed.

Several important ground state properties—structural, elastic, thermodynamic, electronic, magnetic, optical, and thermoelectric properties—of three neodymium-filled skutterudites NdTr₄P₁₂ (Tr = Fe, Ru, and Os) have been investigated using PBE-GGA exchange-correlation potential under the DFT method and Boltzmann transport theory. The effect of changing transition metals on these properties has been explored. Some of the physical parameters increase systematically with increasing atomic number (z) of the transition metals, while some other parameters exhibit a reverse trend. Although the band structure and DOS reveal their metallic nature, near the Fermi level total DOS are different in both spin channels. The materials are ferromagnetic and the magnetic moment of the compounds increases with z. The static dielectric constants also increase with z whereas the refractive indices in the optical frequency range decrease with z. The materials have high reflectivity and low absorption near the Fermi level and within the 0 – 5 eV spectral range, metal-insulator-metal type transition is seen in all. The thermoelectric figure of merit (ZT) increases fast with temperature but shows no systematic variation with z. In the high temperature range NdOs₄P₁₂ shows the maximum ZT value, followed by the ruthenium and iron compounds.

Over the last few years, researchers have been seeking novel oxide materials with room-temperature ferromagnetic properties for use in spintronics devices. In a recent work, we have reported room temperature ferromagnetic correlations in BaBiO₃ nanoparticles which is non-magnetic in its bulk form. Here we have conducted a systematic study of the magnetic behavior by controlled Pb doping. We observe an increase in magnetic saturation for small Pb doping concentration (~ 1%), this is believed to be due to the strain magnetism induced by doping. Upon further increase in the doping concentration, the ferromagnetic behavior has been found diminished in a controlled manner, which indicates the dominance of non-magnetic ion distribution over strain magnetism.

We evaluate the Hall coefficient characterising magnetotransport in an intercalated graphite CaC(_6) with the Fermi surface reconstructed by an uniaxial charge density wave from closed pockets to open sheets. As the typical order parameter, corresponding to the pseudo-gap in electronic spectrum and consequently to spacing between electron trajectories in reciprocal space, is of the order of (10^2)K, magnetic breakdown in strong experimentally achievable fields of the order of 10T is inevitable. The classical expressions for the components of the magnetoconductivity tensor are strongly modified by magnetic field-assisted over-gap tunneling causing quantum interference. Due to magnetic breakdown, all magnetoconductivity components undergo strong quantum oscillations reflected in the Hall coefficient. In their nature, these are different than standard Shubnikov de Haas oscillations which would not appear in a system with an open Fermi surface.

Plant-mediated nanoparticles gaining importance due to their broad spectrum of pharmacological applications in comparison to the synthetic drugs. The nanoparticles amalgamated using plant extracts have been receiving much attention due to the robust phytochemicals and therapeutic potential. Thus, we herein report the biosynthesis and pharmacological evaluation (anti-oxidant, anti-inflammatory, anti-platelet, and anti-cancer properties) of Decalepis hamiltonii leaves extract copper ferrite nanoparticles (DHLE-CuFe₂O₄ NPs). The characterization of DHLE-CuFe₂O₄ NPs was carried out using Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy-dispersive X-ray analysis (EDAX), High-resolution transmission electron microscopy (HR-TEM), and Vibrating sample magnetometer (VSM). DHLE-CuFe₂O₄ NPs exhibited anti-oxidant activity by scavenging 1,1-diphynyl-2-picrylhydrazyl (DPPH) radicals (66.46%) and reduced ferric to ferrous ions at the concentration of 150 μg/mL. Furthermore, DHLE-CuFe₂O₄ NPs restored the NaNO₂-induced oxidative stress markers such as lipid peroxidation, protein carbonyl content, total thiol, and anti-oxidant enzyme (catalase and super oxide dismutase) activities in RBCs. DHLE-CuFe₂O₄ NPs were non-toxic as it did not cause RBCs lysis, while it exhibited anti-inflammatory activity by inhibiting heat-induced hemolysis, egg albumin, and bovine serum albumin denaturation. In addition, DHLE-CuFe₂O₄ NPs inhibited ADP and epinephrine-induced platelet aggregation. Most importantly, DHLE-CuFe₂O₄ NPs showed anti-cancer potential by eliciting cytotoxic effect to MCF-7 cells in a dose-dependent manner. Further, DHLE-CuFe₂O₄ NPs caused apoptosis to MCF-7 cells which was confirmed by annexin V/PI staining test and flow cytometer. In conclusion, DHLE-CuFe₂O₄ NPs regulate oxidative stress-induced red blood cell damage, thrombosis, inflammation, and MCF-7 cells growth.

Two principal physical properties of La₂CuO₄ and YBa₂Cu₃O₆ are identified, which can promote the emergence of superconductivity in unconventional high-temperature superconductors. The first property is a specific type of chemical bonding stimulating fluctuations of the charge density. To reveal it, it is necessary to carry out calculations of the electronic band structure and find the parameters of critical points in the charge density distribution in the crystal. For calculation of the electronic band structure of YBa₂Cu₃O₆ the same approach was applied, which we earlier used for the study of the electronic band structure of La₂CuO₄ and high-temperature superconductors: computer program WIEN2k and exchange potential of Becke and Johnston modified by Tran and Blaha. Such approach allowed us to obtain the antiferromagnetic ground state for the compound YBa₂Cu₃O₆ with a band gap E_g = 1.5 eV and a magnetic moment on copper atoms M_Cu = 0.71 μ_B. It turned out that YBa₂Cu₃O₆ compound has a type of chemical bonding similar to that which we found earlier in La₂CuO₄ and in high-temperature superconductors. Consideration of the symmetry properties of the crystal structures of the La₂CuO₄ and YBa₂Cu₃O₆ compounds revealed a second characteristic property of them – the existence of magnetic crystal classes that admit a linear magnetoelectric effect. This effect allows the simultaneous existence of local magnetic fields and electric polarization in the sample. Based on two identified characteristic physical properties of the La₂CuO₄ and YBa₂Cu₃O₆ compounds, a roadmap is proposed for a search of new parent substances for obtaining unconventional high-temperature superconductors.

The ({J}_{1}-{J}_{2}) frustrated two-dimensional Ising antiferromagnet in the magnetic fields on the square lattice is studied using a functional integral method. First, we determine possible ground states of the model including Néel antiferromagnetic phase and striped antiferromagnetic phase, which depend on the value of the frustrated parameter (alpha ={J}_{2}/{J}_{1}). The influence of the spin fluctuations in the presence of the frustration, temperature, and longitudinal and transverse fields on these two phases is also studied, which shows the strong impact of the spin fluctuations at the phase transition points. The effects of the longitudinal and transverse fields are highlighted. In addition, we also calculate and plot the temperature dependence of the magnetic susceptibility, and we find a sharp peak related to a phase transition and a rounded peak related to the competition of the effects of the antiferromagnetic exchange couplings, temperature and fields. Hence, we suggest experimental relevance for the given theoretical model with Li₂VOSiO₄ and YbBi₂IO₄.

This study employs first-principles calculations to explore the structural, elastic, electronic, magnetic, and optical properties of the quaternary Heusler compounds CoFeYSb (Y = V, Ti). The structural analysis confirms that both compounds are most stable in the YI configuration. CoFeVSb is found to exhibit ferromagnetic behavior, while CoFeTiSb shows ferrimagnetism. Elastic constants, cohesion energy, and formation energy calculations further validate the stability of the magnetic (I) phase for both materials. Band structure analysis reveals that these compounds are half-metallic, achieving 100% spin polarization at the Fermi level, with spin-down energy gaps of 0.55 eV for CoFeVSb and 0.61 eV for CoFeTiSb. The total magnetic moments comply with the Slater-Pauling 24-electron rule, with values of 3 μB for CoFeVSb and 2 μB for CoFeTiSb. Optical investigations, including the dielectric function, absorption coefficient, and energy loss function, demonstrate strong absorption in the visible and ultraviolet ranges. These results highlight the potential of CoFeYSb compounds for advanced optoelectronic and spintronic applications, offering new opportunities for their integration into electronic and photonic technologies.

Sc(0,1,2,3 mol%): Ce: Fe: LiNbO₃ crystals were grown by conventional Czochralski method. The X-ray diffraction is used to determine lattice constants and analyze the internal structure of crystals. The lattice size was found to increase first and then decrease, and the doping elements do not alter the crystal structure. The concentrations of Sc³⁺, Ce⁴⁺, and Fe³⁺ ions in the crystals were measured using ICP-AES. With the increase of Sc³⁺ concentration in the melt, the effective segregation coefficient of Sc³⁺ was found to decrease, while the effective segregation coefficient of Ce⁴⁺ and Fe³⁺ increased. The birefringence gradient of the ScCeFe-3 sample measured using the birefringence gradient method was 3.3 × 10⁻⁵ ∆R/cm⁻¹, which was the best optical homogeneity.